function Person(name, height) {
    this.sayInfo = function() {
        return "姓名：" + name + ", 身高：" + height + ", 体重：" + this.weight;
    }
}
//子类
function Chinese(name, height, weight) {
    console.log(this)
    Person.call(this, name, height);
    this.weight = weight;

    this.nation = function() {
        console.log("我是中国人");
    }
}
//子类
function America(name, height, weight) {
    Person.apply(this, [name, height]);
    this.weight = weight;
}

let chiness = new Chinese("成龙", "178cm", "60kg");
console.log(chiness.sayInfo());    //姓名：成龙, 身高：178cm, 体重：60kg
let america = new America("jack", "180cm", "55kg");
console.log(america.sayInfo());    //姓名：jack, 身高：180cm, 体重：55kg